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Published in:
2011 | OriginalPaper | Chapter
External-Memory Multimaps
Authors : Elaine Angelino, Michael T. Goodrich, Michael Mitzenmacher, Justin Thaler
Published in: Algorithms and Computation
Publisher: Springer Berlin Heidelberg
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Many data structures support dictionaries, also known as maps or associative arrays, which store and manage a set of key-value pairs. A
multimap
is a generalization that allows multiple values to be associated with the same key. For example, the inverted file data structure commonly used in search engines is a type of multimap, with words as keys and document pointers as values. We study the multimap abstract data type and how it can be implemented efficiently online in external memory frameworks, with constant expected I/O performance. The key technique used to achieve our results is a combination of cuckoo hashing using buckets that hold multiple items with a multiqueue implementation to cope with varying numbers of values per key. Our results are provably optimal up to constant factors.